Method for producing hydroxy-L-pipecolic acid

ABSTRACT

A novel method of producing high-purity hydroxy-L-pipecolic acids in an efficient and inexpensive manner while suppressing the production of hydroxy-L-proline is provided. The method includes allowing an L-pipecolic acid hydroxylase, a microorganism or cell having the ability to produce the enzyme, a processed product of the microorganism or cell, and/or a culture liquid comprising the enzyme and obtained by culturing the microorganism or cell, to act on L-pipecolic acid as a substrate in the presence of 2-oxoglutaric acid and ferrous ion, wherein the L-pipecolic acid hydroxylase has the properties:
         (1) the enzyme can act on L-pipecolic acid in the presence of 2-oxoglutaric acid and ferrous ion to add a hydroxy group to the carbon atom at positions 3, 4, and/or 5 of L-pipecolic acid; and   (2) the enzyme has a catalytic efficiency (kcat/Km) with L-proline that is equal to or less than 7 times the catalytic efficiency (kcat/Km) with L-pipecolic acid.

TECHNICAL FIELD

The present invention relates to a method of biologically producing hydroxy-L-pipecolic acids, particularly to a method of producing hydroxy-L-pipecolic acids from L-pipecolic acid based on the use of enzymes that have the ability to produce the hydroxy-L-pipecolic acids.

BACKGROUND ART

Hydroxy-L-pipecolic acids are compounds useful as intermediates to produce pharmaceuticals, and the like. It is known that, for example, (4S)-hydroxy-L-pipecolic acid and (4R)-hydroxy-L-pipecolic acid can be used as precursors of a Rho kinase inhibitor (Patent Document 1) and the HIV protease inhibitor palinavir (Non-Patent Document 1), respectively, while (5S)-hydroxy-L-pipecolic acid and (5R)-hydroxy-L-pipecolic acid can be used as precursors of antimicrobials (Patent Document 2).

It has been known that hydroxy-L-pipecolic acids can be produced from L-pipecolic acid by biological approaches. Examples of proteins having the ability to convert L-pipecolic acid to (5S)-hydroxy-L-pipecolic acid reportedly include the BAB52605 protein derived from the root nodule bacterium Mesorhizobium loti strain MAFF303099 isolated from Lotus japonicus, the CAC47686 protein derived from the root nodule bacterium Sinorhizobium meliloti strain 1021 isolated from Medicago sativa (hereinafter sometimes referred to as “SmPH”), and a protein encoded in a polynucleotide (cistronic gene), the expression of which is initiated 48 nucleotides (corresponding to 16 amino acids) upstream of the translation start site described in the annotation of the EFV12517 protein derived from the Segniliparus rugosus strain ATCC BAA-974 (hereinafter sometimes referred to as “SruPH”), and the like (Patent Document 3). These hydroxylases can be used to convert L-pipecolic acid to hydroxy-L-pipecolic acids.

However, any of these hydroxylases also has the ability to produce hydroxy-L-proline through the hydroxylation of L-proline.

An L-pipecolic acid biologically produced by using an enzyme, microbial bodies, or the like may be contaminated with a trace amount of L-proline, for example, as a carry-over component from a medium used for the preparation of the enzyme or the microbial bodies.

Moreover, in cases where hydroxy-L-pipecolic acids are produced from pure L-pipecolic acid as a base material by using the hydroxylases, the hydroxylases to be used may be contaminated with L-proline.

Furthermore, even if neither L-pipecolic acid as a base material nor the hydroxylases are contaminated with L-proline, in cases where the hydroxylation reaction is achieved by culturing microbial bodies capable of expressing the hydroxylases, L-proline may potentially be produced as a by-product by those microbial bodies during the course of their growth.

Since the physicochemical properties of L-proline are close to those of L-pipecolic acid, it is difficult to obtain pure L-pipecolic acid with complete removal of L-proline.

Moreover, when L-pipecolic acid contaminated with L-proline is used as a base material along with any of the aforementioned enzymes in the conversion of L-pipecolic acid to a hydroxy-L-pipecolic acid, L-proline is converted to hydroxy-L-proline and, therefore, the resulting product will be a mixture of the hydroxy-L-pipecolic acid and hydroxy-L-proline, which makes it difficult to obtain the hydroxy-L-pipecolic acid of high purity. Also, since the physicochemical properties of hydroxy-L-proline are close to those of hydroxy-L-pipecolic acids, it is difficult to separate them from each other.

Accordingly, disadvantageously, a heavy burden in purification process and a huge expense of time and money have been required for the preparation of high-purity hydroxy-L-pipecolic acids with removal of hydroxy-L-proline because multiply repeated purification and use of expensive purification measures are required.

PRIOR ART DOCUMENTS Patent Documents

-   Patent Document 1: JP-T-2010-514720 -   Patent Document 2: JP-T-2004-505088 -   Patent Document 3: WO2013/187438

Non-Patent Document

-   Non-Patent Document 1: Gillard et al., The Journal of Organic     Chemistry, 1996, Vol. 61, pp. 2226

SUMMARY OF THE INVENTION Technical Problem

As described above, methods of biologically producing hydroxy-L-pipecolic acids from L-pipecolic acid are known; however, any of those conventional methods is unsatisfactory as a production method for hydroxy-L-pipecolic acids of high purity, which are used as intermediates of pharmaceuticals, and the like, because not only hydroxy-L-pipecolic acids but also hydroxy-L-proline are produced by those methods. Accordingly, there is a demand for a more efficient production method.

Namely, an object of the present invention is to provide a novel method of producing high-purity hydroxy-L-pipecolic acids in an efficient and inexpensive manner while suppressing the production of hydroxy-L-proline.

Solution to Problem

The inventors intensively studied to solve the above-described problem and consequently found that particular pipecolic acid hydroxylases have the ability to convert L-pipecolic acid to hydroxy-L-pipecolic acids (L-pipecolic acid hydroxylation activity) in a 2-oxoglutarate-dependent fashion and have almost no activity to convert L-proline to hydroxy-L-proline (L-proline hydroxylation activity), and that various hydroxy-L-pipecolic acids with high optical purity can be obtained in a highly efficient manner by allowing those particular enzymes to act on L-pipecolic acid. The present invention was achieved based on these findings.

Now, the spirit of the present invention will be described below.

[1] A method of producing a hydroxy-L-pipecolic acid, the method comprising:

allowing an L-pipecolic acid hydroxylase, a microorganism or cell having the ability to produce the enzyme, a processed product of the microorganism or cell, and/or a culture liquid comprising the enzyme and obtained by culturing the microorganism or cell, to act on L-pipecolic acid as a substrate in the presence of 2-oxoglutaric acid and ferrous ion, wherein the L-pipecolic acid hydroxylase has the properties (1) and (2) below:

(1) the enzyme can act on L-pipecolic acid in the presence of 2-oxoglutaric acid and ferrous ion to add a hydroxy group to the carbon atom at positions 3, 4, and/or 5 of L-pipecolic acid; and

(2) the enzyme has a catalytic efficiency (kcat/Km) with L-proline that is equal to or less than 7 times the catalytic efficiency (kcat/Km) with L-pipecolic acid.

[2] The method of producing a hydroxy-L-pipecolic acid according to [1], further comprising:

allowing L-lysine and/or DL-lysine to react with

-   -   (i-1) one or more enzymes selected from the group consisting of         an L-amino acid oxidase, an L-amino acid dehydrogenase and an         L-amino acid aminotransferase, or     -   (i-2) an amino acid racemase and one or more enzymes selected         from the group consisting of a D-amino acid oxidase, a D-amino         acid dehydrogenase and a D-amino acid aminotransferase,

for the production of 3,4,5,6-tetrahydropyridine-2-carboxylic acid; and subsequently

allowing an N-methyl-L-amino acid dehydrogenase to act on the 3,4,5,6-tetrahydropyridine-2-carboxylic acid for the production of the L-pipecolic acid as the substrate.

[3] The method of producing a hydroxy-L-pipecolic acid according to [1], further comprising:

allowing L-lysine to react with one or more enzymes selected from the group consisting of an L-lysine 6-oxidase, an L-lysine 6-dehydrogenase and an L-lysine 6-aminotransferase, for the production of 2,3,4,5-tetrahydropyridine-2-carboxylic acid; and subsequently

allowing a pyrroline-5-carboxylate reductase to act on the 2,3,4,5-tetrahydropyridine-2-carboxylic acid for the production of the L-pipecolic acid as the substrate.

[4] The method of producing a hydroxy-L-pipecolic acid according to [1], further comprising allowing a lysine cyclodeaminase to act on L-lysine for the production of the L-pipecolic acid as the substrate.

[5] The method of producing a hydroxy-L-pipecolic acid according to any of [1] to [4], wherein the content of L-proline in the L-pipecolic acid as the substrate is not more than 10% (w/w).

[6] The method of producing a hydroxy-L-pipecolic acid according to any of [1] to [5], wherein the L-pipecolic acid hydroxylase further has the property (3) below:

(3) the microorganism or cell having the ability to produce the L-pipecolic acid hydroxylase, or the processed product of the microorganism or cell has a hydroxy-L-proline-producing activity that is not more than 55%, where a ratio of 100% corresponds to the hydroxy-L-pipecolic acid-producing activity of the same microorganism or cell, or of the same processed product.

[7] The method of producing a hydroxy-L-pipecolic acid according to any of [1] to [6], wherein the L-pipecolic acid hydroxylase comprises the protein (A), (B), or (C) below:

(A) a protein having an amino acid sequence represented by SEQ ID NO: 2, 12, 14, 16, 18, or 20;

(B) a protein having the same amino acid sequence as the amino acid sequence represented by SEQ ID NO: 2, 12, 14, 16, 18, or 20 except that one or several amino acids are deleted, substituted, inserted, and/or added, which protein has the aforementioned properties (1) and (2);

(C) a protein having an amino acid sequence with an identity of not less than 80% to the amino acid sequence represented by SEQ ID NO: 2, 12, 14, 16, 18, or 20, which protein has the aforementioned properties (1) and (2).

[8] The method of producing a hydroxy-L-pipecolic acid according to any of [1] to [7], wherein the microorganism or cell having the ability to produce the L-pipecolic acid hydroxylase is a microorganism or cell transformed with DNA encoding the L-pipecolic acid hydroxylase. [9] The method of producing a hydroxy-L-pipecolic acid according to [8], wherein the DNA encoding the L-pipecolic acid hydroxylase comprises the DNA (D), (E), or (F) below:

(D) DNA having a nucleotide sequence represented by SEQ ID NO: 1, 11, 13, 15, 17, or 19;

(E) DNA comprising the same nucleotide sequence as the nucleotide sequence represented by SEQ ID NO: 1, 11, 13, 15, 17, or 19 except that one or several bases are deleted, substituted, inserted, and/or added, which DNA encodes a protein having the aforementioned properties (1) and (2);

(F) DNA comprising a nucleotide sequence which hybridizes with a complementary strand of the nucleotide sequence represented by SEQ ID NO: 1, 11, 13, 15, 17, or 19 under stringent conditions, which DNA encodes a protein having the aforementioned properties (1) and (2).

Advantageous Effects of the Invention

According to the present invention, high-purity hydroxy-L-pipecolic acids with high optical purity can be produced in a highly efficient manner. In particular, according to the present invention, high-purity hydroxy-L-pipecolic acids can be produced even in cases where the L-pipecolic acid as the substrate is contaminated with L-proline.

Furthermore, the present invention is preferable from an industrial viewpoint because the production of hydroxy-L-proline can be reduced and, thus, high-purity hydroxy-L-pipecolic acids available as intermediates for pharmaceuticals, and the like can be produced at low cost and at less expense.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 represents graphs obtained in Example 3 by plotting the reciprocals of the respective concentrations of L-pipecolic acid (mmol/L) on the x-axis and the reciprocals of the hydroxy-L-pipecolic acid-producing activities per milligram of each hydroxylase (U/mg) at the respective concentrations of L-pipecolic acid on the y-axis.

FIG. 2 indicates the reactivity with TL-proline and L-pipecolic acid in L-pipecolic acid 5-hydroxylases compared in Example 4.

FIG. 3 shows the temporal change in amount of accumulated (5S)-hydroxy-L-pipecolic acid in Example 5.

FIG. 4 shows the temporal change in amount of accumulated (4S)-hydroxy-L-pipecolic acid in Example 5.

DESCRIPTION OF THE EMBODIMENTS

Now, the present invention will be described below in detail.

In the present specification, the “L-pipecolic acid hydroxylation activity” means the ability to add a hydroxy group to the carbon atom at positions 3, 4, and/or 5 of L-pipecolic acid.

Whether or not the “L-pipecolic acid hydroxylation activity” is retained in a measurement subject can be confirmed, for example, by allowing an enzyme, which is a measurement subject, to act on L-pipecolic acid in a reaction system containing L-pipecolic acid as a substrate and further containing 2-oxoglutaric acid and ferrous ion, and then measuring the amount of resulting hydroxy-L-pipecolic acid.

The term “enzyme” in the present specification includes a purified enzyme (including a partially purified enzyme), and an immobilized enzyme on a carrier prepared by using a conventional immobilization technique, including, for example, an enzyme immobilized on a carrier such as polyacrylamide and carrageenan gels, and the like.

In the present specification, the term “expression vector” refers to a genetic element that is used for the introduction of a polynucleotide encoding a protein with a desired function into a host organism to be recombined, followed by the replication of the polynucleotide and the expression of the protein with the desired function in the host organism. Examples of the expression vector include, but are not limited to, plasmid, virus, phage, cosmid, and the like, and a preferable example is plasmid.

In the present specification, “transformant” means a microorganism or cell into which a gene of interest has been introduced using an expression vector, such as those as described above, to allow the microorganism or cell to exhibit a desired phenotype associated with an encoded protein with a desired function.

The method of producing a hydroxy-L-pipecolic acid according to the present invention is characterized by allowing an L-pipecolic acid hydroxylase, a microorganism or cell having the ability to produce the enzyme, a processed product of the microorganism or cell, and/or a culture liquid comprising the enzyme and obtained by culturing the microorganism or cell, to act on the L-pipecolic acid as the substrate in the presence of 2-oxoglutaric acid and ferrous ion, wherein the L-pipecolic acid hydroxylase has the properties (1) and (2) below:

(1) the enzyme can act on L-pipecolic acid in the presence of 2-oxoglutaric acid and ferrous ion to add a hydroxy group to the carbon atom at positions 3, 4, and/or 5 of L-pipecolic acid; and

(2) the enzyme has a catalytic efficiency (kcat/Km) with L-proline that is equal to, or less than 7 times the catalytic efficiency (kcat/Km) with L-pipecolic acid.

The L-pipecolic acid hydroxylase used in the present invention (hereinafter sometimes referred to as “L-pipecolic acid hydroxylase of the present invention”) is an enzyme capable of acting on L-pipecolic acid in the presence of 2-oxoglutaric acid and ferrous ion to add a hydroxy group to the carbon atom at positions 3, 4, and/or 5 of L-pipecolic acid.

The amount of 2-oxoglutaric acid is not particularly limited as long as it is not an amount so as to inhibit the reaction, but it is normally an amount equimolar to or greater than the amount of L-pipecolic acid in the reaction system and is preferably an amount ranging from 1 to 1.2 times the number of moles of L-pipecolic acid in the reaction system.

The amount of ferrous ion is not particularly limited as long as it is not an amount so as to inhibit the reaction, but it normally from 0.0001 to 0.5 mol, preferably from 0.001 to 0.1 mol, per mol of L-pipecolic acid in the reaction system.

The addition of, for example, ferrous sulfate, ferrous chloride, ferrous citrate, and the like allows ferrous ions to exist in the reaction system.

The L-pipecolic acid hydroxylase of the present invention preferably includes a protein having an amino acid sequence represented by SEQ ID NO: 2, 12, 14, 16, 18, or 20.

Moreover, the L-pipecolic acid hydroxylase of the present invention may include a protein having an amino acid sequence homologous to the amino acid sequence represented by SEQ ID NO: 2, 12, 14, 16, 18, or 20, which is a protein having the L-pipecolic acid hydroxylation activity and the properties (1) and (2) as described above.

Such a protein having an amino acid sequence homologous to the amino acid sequence represented by SEQ TD NO: 2, 12, 14, 16, 18, or 20 includes a protein having the same amino acid sequence as the amino acid sequence represented by SEQ ID NO: 2, 12, 14, 16, 18, or 20 except that one or several amino acids are deleted, substituted, inserted, and/or added. In the case of substitution, insertion, or addition, conservative mutations resulting from conservative substitution, insertion, or addition of one or several amino acids are preferable.

The phrase “one or several amino acids” herein means usually 1 to 100, preferably 1 to 50, more preferably 1 to 20, still more preferably 1 to 10, particularly preferably 1 to 5, amino acids.

Moreover, the protein having an amino acid sequence homologous to the amino acid sequence represented by SEQ ID NO: 2, 12, 14, 16, 18, or 20 includes a protein having an amino acid sequence with an identity of not less than 70% to the amino acid sequence represented by SEQ ID NO: 2, 12, 14, 16, 18, or 20 in its full-length form. The protein includes a protein having an amino acid sequence with an identity of preferably not less than 80%, more preferably not less than 90%, and still more preferably not less than 95% to the above-described amino acid sequence in its full-length form.

In the present invention, the term “sequence identity” means, in nucleotide sequences or amino acid sequences, the percentage of identical nucleotides or amino acids shared between two sequences, which percentage is determined by aligning those two sequences in an optimal pairwise alignment. That is, the identity can be calculated with the formula below and can be calculated by using a commercially available algorithm: Identity−(the number of matches at each position/the total number of positions)×100.

Moreover, such algorithms are incorporated in NBLAST and XBLAST programs as described in Altschul et al., J. Mol. Biol. 215 (1990) pp. 403-410. More particularly, the identity search and the identity analysis can be performed on nucleotide sequences or amino acid sequences by means of algorithms or programs well known to those skilled in the art (for example, BLASTN, BLASTP, BLASTX, ClustalW). Parameters for use with a program can be appropriately set by those skilled in the art and default parameters for each program may also be used. Specific procedures in those analysis methods are well known to those skilled in the art.

The amino acid sequences represented by SEQ ID NO: 2, 12, 14, 16, and 18 are based on the genome information of Micromonospora chokoriensis, the Colletotrichum gloeosporioides strain Nara qc5, the Penicillium chrysogenum strain Wisconsin 54-1255, the Gibberella zeae strain PH-1, and a Kordia jejudonensis strain, respectively.

Among those L-pipecolic acid hydroxylases of the present invention, the protein having the amino acid sequence represented by SEQ ID NO: 2, 18, or 20, and the protein having an amino acid sequence homologous to the amino acid sequence represented by SEQ ID NO: 2, 18, or 20 and having the L-pipecolic acid hydroxylation activity selectively hydroxylates the carbon atom at position 5 of L-pipecolic acid and therefore they can produce (5S)-hydroxy-L-pipecolic acid with high efficiency.

Among those L-pipecolic acid hydroxylases of the present invention, the protein having the amino acid sequence represented by SEQ ID NO: 12, 14, or 16, and the protein having an amino acid sequence homologous to the amino acid sequence represented by SEQ ID NO: 12, 14, or 16 and having the L-pipecolic acid hydroxylation activity selectively hydroxylates the carbon atom at position 4 of L-pipecolic acid and therefore they can produce (4S)-hydroxy-L-pipecolic acid with high efficiency.

In the present invention, one, two or more types of L-pipecolic acid hydroxylases can be used.

The L-pipecolic acid hydroxylase of the present invention can be obtained by purification from Micromonospora chokoriensis, the Colletotrichum gloeosporioides strain Nara qc5, the Penicillium chrysogenum strain Wisconsin 54-1255, the Gibberella zeae strain PH-1, the Kordia jejudonensis strain, or the like.

Also, the L-pipecolic acid hydroxylase of the present invention can be obtained by cloning a DNA encoding the L-pipecolic acid hydroxylase of the present invention by means of known methods including PCR (polymerase chain reaction), hybridization, and the like, and then allowing the L-pipecolic acid hydroxylase to be expressed in an appropriate host.

The DNAs encoding L-pipecolic acid hydroxylases comprising the proteins having the amino acid sequences represented by SEQ ID NO: 2, 12, 14, 16, 18, and 20 respectively correspond to, for example, DNAs comprising the nucleotide sequences represented by SEQ ID NO: 1, 11, 13, 15, 17, and 19. Moreover, the DNA may be a DNA homologous to the above DNA comprising the nucleotide sequence represented by SEQ ID NO: 1, 11, 13, 15, 17, or 19, which encodes a protein having the L-pipecolic acid hydroxylation activity and the properties (1) and (2) as described above.

Such a DNA homologous to the above DNA comprising the nucleotide sequence represented by SEQ ID NO: 1, 11, 13, 15, 17, or 19 includes a DNA comprising the same nucleotide sequence as the nucleotide sequence represented by SEQ ID NO: 1, 11, 13, 15, 17, or 19 except that one or several bases are deleted, substituted, inserted, and/or added. In the case of substitution, insertion, or addition, conservative mutations resulting from conservative substitution, insertion, or addition of one or several bases are preferable.

The phrase “one or several bases” herein means usually 1 to 300, preferably 1 to 150, more preferably 1 to 60, still more preferably 1 to 30, more preferably 1 to 15, particularly preferably 1 to 10, bases.

The nucleotide sequences represented by SEQ ID NO: 1, 11, 13, 15, and 17 respectively correspond to the nucleotide sequences of genes originated from Micromonospora chokoriensis, the Colletotrichum gloeosporioides strain Nara qc5, the Penicillium chrysogenum strain Wisconsin 54-1255, the Gibberella zeae strain PH-1, and the Kordia jejudonensis strain, which nucleotide sequences are codon-optimized for E. coli expression and encode the amino acid sequences represented by SEQ ID NO: 2, 12, 14, 16, and 18. Such a DNA with codon-optimization according to the host for transformation is, of course, included in examples of the DNA encoding the L-pipecolic acid hydroxylase of the present invention.

Moreover, the DNA homologous to the above DNA comprising the nucleotide sequence represented by SEQ ID NO: 1, 11, 13, 15, 17, or 19 may be a DNA comprising a nucleotide sequence which hybridizes with the complementary strand of the nucleotide sequence represented by SEQ ID NO: 1, 11, 13, 15, 17, or 19 under stringent conditions.

The phrase “nucleotide sequence which hybridizes under stringent conditions” herein means the nucleotide sequence of a DNA that is obtained by using a DNA probe and using colony hybridization, plaque hybridization, Southern blot hybridization, or the like under stringent conditions.

Examples of the stringent conditions include, in cases of colony hybridization or plaque hybridization, conditions where filters with immobilized DNA from colonies or plaques, or with immobilized DNA fragments thereof are used to perform hybridization at 65° C. in the presence of 0.7 mol/L to 1 mol/L aqueous solution of sodium chloride, and the filters are subsequently washed under a temperature condition of 65° C. by using 0.1×SSC solution (the composition of 1×SSC: 150 mmol/L aqueous solution of sodium chloride, 15 mmol/L aqueous solution of sodium citrate). Such hybridization can be performed in accordance with the methods described in Molecular Cloning: A laboratory Manual, 2^(nd) Ed., Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y., 1989, and the like.

Those skilled in the art will be able to introduce a desired mutation into the DNA comprising the nucleotide sequence represented by SEQ ID NO: 1, 11, 13, 15, 17, or 19 by deletion, substitution, insertion, and/or addition of one or more bases by means of site-directed mutagenesis (Nucleic Acids Res. 10, pp. 6487 (1982); Methods in Enzymol. 100, pp. 448 (1983); Molecular Cloning; PCR: A Practical Approach, IRL Press, pp. 200 (1991)) and the like to provide a mutant DNA of the DNA comprising the nucleotide sequence represented by SEQ ID NO: 1, 11, 13, 15, 17, or 19.

Moreover, the amino acid information of the L-pipecolic acid hydroxylase of the present invention or the nucleotide sequence information of a DNA encoding the same may be obtained by a homology search of the entire or part of the amino acid sequence represented by SEQ ID NO: 2, 12, 14, 16, 18, or 20, or the entire or part of the nucleotide sequence represented by SEQ ID NO: 1, 11, 13, 15, 17, or 19, against databases such as DNA Databank of JAPAN (DDBJ).

Moreover, the L-pipecolic acid hydroxylase of the present invention has a catalytic efficiency (kcat/Km) with L-proline that is equal to, or less than 7 times, preferably equal to, or less than 2 times, more preferably equal to, or less than 1 time, still more preferably equal to, or less than 0.5 times, and particularly preferably equal to, or less than 0.1 times the catalytic efficiency (kcat/Km) with L-pipecolic acid. An L-pipecolic acid hydroxylase exhibiting virtually no hydroxy-L-proline-producing activity is most preferable. The phrase “virtually no hydroxy-L-proline-producing activity” in the present invention does not mean not producing even one molecule of hydroxy-L-proline but means producing an undetectable amount of, or a detectable but trace amount of hydroxy-L-proline, which is almost a negligible amount based on the common knowledge of those skilled in the art.

The catalytic efficiency (kcat/Km) in the present invention can be determined, for example, by a method using the Michaelis-Menten kinetic equation to calculate the kcat/Km value. Herein, the term “kcat” refers to the catalytic efficiency per molecule of an enzyme, while the term “Km” is an index representing the affinity of the enzyme with its substrate.

A specific method to calculate Km and kcat is as described below. First, the hydroxy-L-pipecolic acid-producing activity per milligram of each hydroxylase (U/mg) at each concentration of L-pipecolic acid is measured in a particular range of substrate concentration. One unit (U) herein represents the ability to produce 1 μmol of a hydroxy-L-pipecolic acid in the period of 1 minute. Subsequently, the reciprocals of the respective concentrations of L-pipecolic acid (mmol/L) and the reciprocals of the hydroxy-L-pipecolic acid-producing activities per milligram of the hydroxylase (U/mg) at the respective concentrations of L-pipecolic acid are plotted on the x-axis and the y-axis, respectively. It is known that, in those linear plots, the reciprocal of each intercept with the x-axis, multiplied with −1, represents a km value (mmol/L) and the reciprocal of each intercept with the y-axis represents a Vmax value (U/mg), the maximum rate of reaction. The catalytic ability per molecule of the enzyme (kcat) can be calculated from the Vmax and the molecular weight of the enzyme. The thus-obtained kcat and km values can be used to calculate the catalytic efficiency (kcat/Km), which is an index representing the catalytic ability of the enzyme.

As an enzyme to be used for the calculation of the catalytic efficiency, a crudely or finely purified material containing an enzyme fraction extracted from the microorganism or cell having the ability to produce the enzyme, which are disrupted by treatment with an organic solvent, a surfactant, and the like, and/or by physical or enzymatic treatment, can be used. The level of the enzymatic activity and the reaction time can be set as desired to the extent that the enzymatic activity is increased proportionally to the amount of the reaction time.

Details of the Michaelis-Menten equation and the like are described in, for example, “Biochemical Research Methods, Vol. 21: Guide to Experiments on Enzymatic Reaction Kinetics, Gakkai Shuppan Center, Ltd.” and the like.

Furthermore, the L-pipecolic acid hydroxylase activity in the present invention may also be simply evaluated by the following procedures.

The microorganism or cell having the ability to produce the L-pipecolic acid hydroxylase of the present invention, or the processed product of the microorganism or cell is allowed to react with L-pipecolic acid or L-proline and then the hydroxy-L-pipecolic acid-producing activity (U/g) and the hydroxy-L-proline-producing activity (U/g) per amount of inputted cells (unit: gram (g) or turbidity) or per mass of total proteins (unit: g) are measured in particular substrate concentrations. Then, the activity to produce hydroxy-L-proline from L-proline at a particular substrate concentration (relative value) is calculated, where a ratio of 100% corresponds to the activity to produce a hydroxy-L-pipecolic acid from L-pipecolic acid at the same substrate concentration.

As for the L-pipecolic acid hydroxylase of the present invention, the activity to produce hydroxy-L-proline in the microorganism or cell having the ability to produce the L-pipecolic acid hydroxylase, or in the processed product of the microorganism or cell is normally not more than 55%, preferably not more than 50%, more preferably not more than 35%, particularly preferably not more than 20%, and most preferably 0% relative, where a ratio of 100% corresponds to the activity to produce a hydroxy-L-pipecolic acid in the microorganism or cell having the ability to produce the enzyme, or in the processed product of the microorganism or cell.

Because the L-pipecolic acid hydroxylase used in the present invention (hereinafter sometimes referred to as “L-pipecolic acid hydroxylase of the present invention”) can hydroxylate L-pipecolic acid with high regiospecificity and high stereospecificity, hydroxy-L-pipecolic acids with high optical purity can be obtained with high efficiency.

In the method of producing a hydroxy-L-pipecolic acid according to the present invention, the L-pipecolic acid hydroxylase of the present invention may be directly used for the reaction, or a microorganism or cell having the ability to produce the enzyme, a processed product of the microorganism or cell, and/or a culture liquid comprising the enzyme and obtained by culturing the microorganism or cell may be used for the reaction.

The microorganism or cell having the ability to produce the L-pipecolic acid hydroxylase of the present invention may be a microorganism or cell inherently having the above production ability, or a microorganism or cell on which the above production ability has been conferred by breeding. Moreover, the microorganism or cell having the ability to produce the L-pipecolic acid hydroxylase of the present invention is not limited to a living microorganism or cell but includes those apparently dead as living bodies and retaining the ability of the enzyme.

Moreover, the types of microorganisms or cells having the ability to produce an L-pipecolic acid hydroxylase include those described below as “host microorganisms” or “host cells”.

Known methods such as recombinant gene technology (transformation) and mutagenesis may be employed as the means to impart the above production ability by breeding. Several different methods may be used as the method of transformation, in which the expression of a gene of interest on DNA is enhanced by introducing DNA carrying the gene of interest, by modifying an expression regulatory sequence of the gene, such as a promoter, on the chromosome, or the like.

Among them, it is preferred to use a microorganism or cell which has been transformed with a DNA encoding the L-pipecolic acid hydroxylase of the present invention.

For example, a DNA encoding the L-pipecolic acid hydroxylase of the present invention is operatively inserted into a known expression vector to construct an L-pipecolic acid hydroxylase-expressing vector, and the expression vector is used to transform a host cell. Thus, a transformant into which the DNA encoding the L-pipecolic acid hydroxylase of the present invention has been introduced can be produced.

Moreover, the transformant can also be produced by incorporation of the DNA encoding the L-pipecolic acid hydroxylase of the present invention into a chromosome of the host cell in such a way that expression of the enzyme is possible, which incorporation is mediated by a procedure such as homologous recombination or the like.

The procedure for establishing the transformant, the method of constructing a recombinant vector suitable for the host, and the method of culturing the host can be carried out in accordance with techniques conventionally used in the fields of molecular biology, bioengineering and genetic engineering (for example, methods described in Molecular Cloning, supra).

Examples of the method of preparing the transformant include a method in which the DNA encoding the L-pipecolic acid hydroxylase of the present invention is introduced into a plasmid vector, phage vector, or virus vector that stably exists in a host cell and then the constructed expression vector is introduced into the host cell, or a method in which the DNA is directly introduced into the host genome, in both of which methods the genetic information on the DNA is then transcribed and translated.

In this process, it is preferable to link a promoter to the DNA on the 5′-upstream side and it is more preferable to further link a terminator to the DNA on the 3′-downstream side, which promoter and terminator are suitable in the host. As long as the promoter and the terminator are a promoter and a terminator which are known to be functional in a host, they can be used and are not particularly limited. For example, vectors, promoters, and terminators described in “Fundamental Microbiology 8: Genetic Engineering, Kyoritsu Shuppan Co., Ltd.” can be used.

The host microorganism or host cell to be transformed is not particularly limited as long as the host itself does not adversely affect the reaction of L-pipecolic acid.

Examples of the host microorganism include prokaryotes such as E. coli (bacteria of the genus Escherichia), bacteria of the genus Bacillus, bacteria of the genus Pseudomonas, coryneform bacteria, root-nodule bacteria, bacteria of the genus Lactobacillus, bacteria of the genus Brevibacillus, bacteria of the genus Anaerobiospirillum, bacteria of the genus Actinobacillus, actinomycetes, and the like; and eukaryotes including fungi, such as yeasts and filamentous fungi, plants, animals, and the like. Among them, E. coli, yeasts, and coryneform bacteria are preferable, and E. coli is particularly preferable.

Examples of the host microorganism include microorganisms as described below:

bacteria belonging to the genera Escherichia, Bacillus, Pseudomonas, Corynebacterium, Rhizobiun, Lactobacillus. Brevibacillus, Anaerobiospirillum, Actinobacillus, Serratia, Brevibacterium, Streptococcus, and the like, whose host vector systems have been established:

actinomycetes belonging to the genera Rhodococcus, Streptomyces, and the like, whose host vector systems have been established;

yeasts belonging to the genera Saccharomyces, Kluyveromyces, Schizosaccharomyces, Zygosaccharomyces, Yarrowia, Trichosporon, Rhodosporidium, Hansenula, Pichia, Candida, and the like, whose host vector systems have been established; and

fungi belonging to the genera Neurospora, Aspergillus, Cephalosporium, Trichoderma, and the like, whose host vector systems have been established.

Examples of preferable host microorganisms and of a preferable transformation procedure, vector, promoter, and terminator for each microorganism will be described below. However, the present invention is not limited thereto.

For the genus Escherichia, especially Escherichia coli, examples of the plasmid vector include plasmids of the pBR series, the pUC series, and the like; and examples of the promoter include lac (β-galactosidase), frp (tryptophan operon), tac, trc (a fusion of lac and trp), the PL and PR promoters of phage lambda, promoters derived from T7 phage, and the like. Moreover, examples of the terminator include terminators derived from trpA, phages, and rrnB ribosomal RNA, and the like. Among those promoters, a promoter that allows inducible gene expression may also be used for the purpose of improving the expression efficiency. For example, in the case of the above lac promoter, gene expression can be induced by addition of an inducer such as lactose or isopropyl-β-D-thiogalactoside (IPTG).

For the genus Bacillus, examples of the vector can include plasmids based on pUB110, pC194, and the like, which may be integrated into a chromosome. As the promoter and the terminator, those of genes for enzymes, such as alkaline protease, neutral protease, and α-amylase, can be used.

For the genus Pseudomonas, examples of the vector can include generic host vector systems established in Pseudomonas putida, Pseudomonas cepacia, and the like; the wide-host-range vector pKT240 (containing genes required for autonomous replication and derived from RSF1010 and the like), which is based on a plasmid involved in degradation of toluene compounds, TOL plasmid (Gene, 26, 273-82 (1983)); and the like.

For the genus Brevibacterium, especially Brevibacterium lactofermentum, examples of the vector can include plasmid vectors such as pAJ43 (Gene, 39, 281 (1985)). As the promoter and the terminator, various promoters and terminators used in E. coli can be used.

For the genus Corynebacterium, especially Corynebacterium glutamicum, examples of the vector include plasmid vectors such as pCS11 (JP-57-183799 A) and pCB101 (Mol. Gen. Genet., 196, 175 (1984)).

For Saccharomyces, especially Saccharomyces cerevisiae, examples of the vector include plasmids of the YRp series, the YEp series, the YCp series, and the YIp series, and the like. Moreover, examples of promoters and terminators which may be used include those of the genes for various enzymes such as alcohol dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase, acid phosphatase, β-galactosidase, phosphoglycerate kinase, and enolase.

For the genus Schizosaccharomyces, examples of the vector can include plasmid vectors, such as the plasmid vectors derived from Schizosaccharomyces pombe described in Mol. Cell. Biol., 6, 80 (1986). In particular, pAUR224 is commercially available from Takara Shuzo Co., Ltd. and readily available.

In the genus Aspergillus, Aspergillus niger, Aspergillus oryzae and the like are the best-studied species among molds, in which plasmids and integration into the chromosome are applicable, and promoters for extracellularly secreted protease and amylase can be used (Trends in Biotechnology, 7, 283-287 (1989)).

Moreover, examples of the host cell include cells from animals, such as insects (for example, silkworm) (Nature, 315, 592-594 (1985)), and from plants such as rapeseed, maize, and potato. Also, cell-free protein synthesis system from E. coli cell-free extract, wheat germ and the like has been established and may preferably be used.

Moreover, various host vector systems other than the above-described systems have also been established, and those systems may be used as appropriate.

In the present specification, a “processed product of the microorganism or cell having the ability to produce an L-pipecolic acid hydroxylase” refers to a product that is prepared by culturing the microorganism or cell having the ability to produce an L-pipecolic acid hydroxylase, and then 1) treating the microorganism or cell with an organic solvent, surfactant, and the like, 2) freeze-drying the microorganism or cell, 3) immobilizing the microorganism or cell on a carrier and the like, 4) physically or enzymatically disrupting the microorganism or cell, or 5) separating an enzyme fraction as a crudely or finely purified material from any of the products of the aforementioned treatments 1) to 4).

Examples of the organic solvent include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, tert-butanol, acetone, dimethyl sulfoxide, ethyl acetate, butyl acetate, toluene, chloroform, n-hexane, and the like.

Examples of the surfactant include nonionic surfactants, such as Tween-20, Triton X-100, Brij 35, dodecyl-β-D-maltoside, Nonidet P-40, and octyl-β-D-glucoside; amphoteric-ionic surfactants, such as 3-(3-cholamidopropyl)dimethylammonio-1-propanesulfonate (CHAPS); anionic surfactants, such as sodium dodecyl sulfate (SDS); and the like.

Specific examples of a procedure to immobilize the microorganism or cell on a carrier and the like include procedures to immobilize an enzyme fraction from the microorganism or cell on a carrier, and other procedures, where representative examples of the carrier include polyacrylamide gel, carrageenan gel, ion exchange resins, and the like.

Examples of a procedure to physically disrupt the microorganism or cell include sonication, high-pressure treatment with French Press, mechanical milling treatment using a homogenizer, Dyno-Mill bead mill, or the like, and other procedures.

Examples of a procedure to enzymatically disrupt the microorganism or cell include a procedure based on the treatment with an enzyme having the cell wall lysis activity, such as lysozyme or the like.

As a separation procedure in the enzyme purification, a conventional procedure for enzyme isolation and purification may be used. For example, a purified material can be separated from the extract prepared by any of the aforementioned procedures or the like, using each or a combination of centrifugation, ultrafiltration, salting-out with ammonium sulfate or the like, desalting, precipitation with an organic solvent, chromatography using various resins (anion exchange chromatography, cation exchange chromatography, hydrophobic chromatography, gel filtration, affinity chromatography), electrophoresis such as isoelectric focusing or the like, and the like.

Examples of the culture liquid comprising the L-pipecolic acid hydroxylase of the present invention and obtained by culturing the microorganism or cell having the ability to produce the enzyme include a suspension of the microorganism or cell and a liquid medium; and in cases where the microorganism or cell is a microorganism or cell for secretory expression, the supernatant obtained by removing the microorganism or cell by centrifugation and the like, and a concentrate of the supernatant; and the like.

In the present specification, a “culture liquid comprising the L-pipecolic acid hydroxylase and obtained by culturing the microorganism or cell having the ability to produce the enzyme” refers to 1) a culture liquid of the microorganism or cell, 2) a culture liquid obtained by treating the culture liquid of the microorganism or cell with an organic solvent, a surfactant, and the like, and 3) a culture liquid in which the cell membrane of the microorganism or cell has been physically or enzymatically disrupted.

As the organic solvent, surfactant, and the physical or enzymatic disruption method, the above-described materials and procedures can be used.

The method of producing a hydroxy-L-pipecolic acid according to the present invention is characterized by allowing an L-pipecolic acid hydroxylase, a microorganism or cell having the ability to produce the enzyme, a processed product of the microorganism or cell, and/or a culture liquid comprising the enzyme and obtained by culturing the microorganism or cell to act on the L-pipecolic acid as the substrate in the presence of 2-oxoglutaric acid and ferrous ion, and thereby producing a hydroxy-L-pipecolic acid.

In the present invention, as the L-pipecolic acid as the substrate, pure L-pipecolic acid may be used and L-pipecolic acid containing a trace amount of L-proline may also be used. The content of L-proline is normally not more than 10% (w/w), preferably not more than 1% (w/w), and particularly preferably not more than 0.1% (w/w).

Moreover, as the L-pipecolic acid as the substrate, a commercial L-pipecolic acid may be used and an L-pipecolic acid biologically produced by using an enzyme, microbial bodies, and the like may also be used. Biologically produced L-pipecolic acid may be contaminated with L-proline, for example, as a carry-over component from a medium used for the preparation of the enzyme or the microbial bodies; in the present invention, L-pipecolic acid can be contaminated with the above-described content of L-proline.

Examples of a method of biologically producing L-pipecolic acid include the methods as described below:

(i) allowing L-lysine and/or DL-lysine to react with

-   -   (i-1) one or more enzymes selected from the group consisting of         an L-amino acid oxidase, an L-amino acid dehydrogenase and an         L-amino acid aminotransferase, or     -   (i-2) an amino acid racemase and one or more enzymes selected         from the group consisting of a D-amino acid oxidase, a D-amino         acid dehydrogenase and a D-amino acid aminotransferase,

for the production of 3,4,5,6-tetrahydropyridine-2-carboxylic acid; and subsequently

allowing an N-methyl-L-amino acid dehydrogenase to act on the 3,4,5,6-tetrahydropyridine-2-carboxylic acid for the production of L-pipecolic acid;

(ii) allowing L-lysine to react with one or more enzymes selected from the group consisting of an L-lysine 6-oxidase, an L-lysine 6-dehydrogenase and an L-lysine 6-aminotransferase, for the production of 2,3,4,5-tetrahydropyridine-2-carboxylic acid; and subsequently

allowing a pyrroline-5-carboxylate reductase to act on the 2,3,4,5-tetrahydropyridine-2-carboxylic acid for the production of L-pipecolic acid; and

(iii) allowing a lysine cyclodeaminase to act on L-lysine for the production of L-pipecolic acid.

The first method of producing L-pipecolic acid in the present invention is a production method as described below, the production method characterized by:

(i) allowing L-lysine and/or DL-lysine to react with

-   -   (i-1) one or more enzymes selected from the group consisting of         an L-amino acid oxidase, an L-amino acid dehydrogenase and an         L-amino acid aminotransferase, or     -   (i-2) an amino acid racemase and one or more enzymes selected         from the group consisting of a D-amino acid oxidase, a D-amino         acid dehydrogenase and a D-amino acid aminotransferase,

for the production of 3,4,5,6-tetrahydropyridine-2-carboxylic acid; and subsequently

allowing an N-methyl-L-amino acid dehydrogenase to act on the 3,4,5,6-tetrahydropyridine-2-carboxylic acid for the production of L-pipecolic acid.

The method will be described below by illustrating a scheme.

In Scheme (i-1), at least one enzyme selected from the group consisting of an L-amino acid oxidase, an L-amino acid dehydrogenase and an L-amino acid transferase, and an N-methyl-L-amino acid dehydrogenase (NMAADH) are used.

First, the compound (a) (L-lysine) is converted to the compound (b) by an enzyme selected from the group consisting of an L-amino acid oxidase, an L-amino acid dehydrogenase and an L-amino acid transferase. The compound (b) is spontaneously converted to the compound (c) (3,4,5,6-tetrahydropyridine-2-carboxylic acid). Then, the compound (c) is converted to the compound (d) (L-pipecolic acid) by an N-methyl-L-amino acid dehydrogenase (NMAADH, also known as DpkA).

Here, the L-amino acid oxidase is not particularly limited as long as it is an enzyme which can catalyze the substitution of the amino group at position 2 of L-lysine with an oxo group, but examples of the L-amino acid oxidase include a protein as described in J. Biochem., 2015, 157 (4), pp. 201, or proteins each having an amino acid sequence with an identity of not less than 80%, preferably not less than 90%, and more preferably not less than 95% to the amino acid sequence of the above protein and maintaining the activity thereof.

The L-amino acid dehydrogenase is not particularly limited as long as it is an enzyme which can catalyze the substitution of the amino group at position 2 of L-lysine with an oxo group, but examples of the L-amino acid dehydrogenase include a protein as described in Nature, 1966, 211, pp. 854, or proteins each having an amino acid sequence with an identity of not less than 80%, preferably not less than 90%, and more preferably not less than 95% to the amino acid sequence of the above protein and maintaining the activity thereof.

The L-amino acid transferase (L-amino acid aminotransferase) is not particularly limited as long as it is an enzyme which can catalyze the substitution of the amino group at position 2 of L-lysine with an oxo group, but examples of the L-amino acid transferase include a protein containing an amino acid sequence as described in Eur. J. Biochem., 1998, 254, pp. 347, or proteins each having an amino acid sequence with an identity of not less than 80%, preferably not less than 90%, and more preferably not less than 95% to the amino acid sequence of the above protein and maintaining the activity thereof.

The N-methyl-L-amino acid dehydrogenase is not particularly limited as long as it is an enzyme which can catalyze the conversion of 3,4,5,6-tetrahydropyridine-2-carboxylic acid to L-pipecolic acid, but examples of the N-methyl-L-amino acid dehydrogenase include DpkA described in J. Biol. Chem. 2005, 280(49), pp. 40875, or proteins each having an amino acid sequence with an identity of not less than 80%, preferably not less than 90%, and more preferably not less than 95% to the amino acid sequence of DpkA and maintaining the activity thereof.

In Scheme (i-2), at least one enzyme selected from the group consisting of a D-amino acid oxidase, a D-amino acid dehydrogenase and a D-amino acid transferase, an amino acid racemase, and an N-methyl-L-amino acid dehydrogenase (NMAADH) are used.

First, the compound (a) (L-lysine) is converted to the compound (a′) in the D-form (D-lysine) by an amino acid racemase, which is then converted to the compound (b) by an enzyme selected from the group consisting of a D-amino acid oxidase, a D-amino acid dehydrogenase and a D-amino acid transferase. The compound (b) is spontaneously converted to the compound (c). Then, the compound (c) is converted to the compound (d) (L-pipecolic acid) by an N-methyl-L-amino acid dehydrogenase (NMAADH).

The D-amino acid oxidase is not particularly limited as long as it is an enzyme which catalyze the substitution of the amino group at position 2 of D-lysine with an oxo group, but examples of the D-amino acid oxidase include a protein containing an amino acid sequence as described in Biochemistry, 2005, 70, pp. 40, or proteins each having an amino acid sequence with an identity of not less than 80%, preferably not less than 90%, and more preferably not less than 95% to the amino acid sequence of the above protein and having the activity thereof.

The D-amino acid dehydrogenase is not particularly limited as long as it is an enzyme which catalyze the substitution of the amino group at position 2 of D-lysine with an oxo group, but examples of the D-amino acid dehydrogenase include DauA described in Microbiology, 2010, 156 (Pt 1), pp. 60 and Proc. Natl. Acad. Sci. U.S.A., 2009, 106, pp. 906, or proteins each having an amino acid sequence with an identity of not less than 80%, preferably not less than 90%, and more preferably not less than 95% to the amino acid sequence of DauA and maintaining the activity thereof.

The D-amino acid transferase (D-amino acid aminotransferase) is not particularly limited as long as it is an enzyme which catalyze the substitution of the amino group at position 2 of D-lysine with an oxo group, but examples of the D-amino acid transferase include D-AAT described in Protein Eng, 1998, 11, pp. 53, or proteins each having an amino acid sequence with an identity of not less than 80%, preferably not less than 90%, and more preferably not less than 95% to the amino acid sequence of D-AAT and maintaining the activity thereof.

The amino acid racemase (LysR) is not particularly limited as long as it is an enzyme which can catalyze the conversion of L-lysine to D-lysine, but examples of the amino acid racemase include LysR described in Appl. Microbiol. Biotechnol. 2015, 99, pp. 5045, or proteins each having an amino acid sequence with an identity of not less than 80%, preferably not less than 90%, and more preferably not less than 95% to the amino acid sequence of LysR and maintaining the activity thereof.

The N-methyl-L-amino acid dehydrogenase is not particularly limited as long as it is an enzyme which can catalyze the conversion of 3,4,5,6-tetrahydropyridine-2-carboxylic acid to L-pipecolic acid, but examples of the N-methyl-L-amino acid dehydrogenase include DpkA described in J. Biol. Chem. 2005, 280(49). pp. 40875, or proteins each having an amino acid sequence with an identity of not less than 80%, preferably not less than 90%, and more preferably not less than 95% to the amino acid sequence of DpkA and maintaining the activity thereof.

In the reactions indicated by Schemes (i-1) and (i-2), each step of the enzyme reaction may be separately performed, but it is preferred to sequentially perform the enzyme reaction steps in the same reaction system.

In cases where the above method is carried out continuously in the same reaction system, the method is preferably carried out in an aqueous medium containing L-lysine and cells transformed with a group of genes encoding the respective enzymes, products prepared from the transformants, and/or culture liquids obtained by culturing the transformants, or alternatively in a mixture of the aqueous medium and an organic solvent.

Because N-methyl-L-amino acid dehydrogenase (NMAADH) requires NAD(P)H as a coenzyme, it is preferred to allow a system for the regeneration of NAD(P)H from NAD(P)+, which is generated in the reaction of NMAAH, to coexist in the same reaction system.

Exemplary methods for regeneration of NAD(P)H include 1) a method in which the ability of a host microorganism itself to reduce NAD(P)⁺ is utilized; 2) a method in which a microorganism having the ability to generate NAD(P)H from NAD(P) or a product prepared therefrom, or an enzyme available for the regeneration of NAD(P)H (regeneration enzyme), such as glucose dehydrogenase, formate dehydrogenase, alcohol dehydrogenase, an amino acid dehydrogenase, or an organic acid dehydrogenase (such as malate dehydrogenase), is added to the reaction system; 3) a method in which genes for the above regeneration enzymes available for the regeneration of NAD(P)H are introduced together with the DNA according to the present invention into a host; and the like.

Among them, in the above-described regeneration method (1), compounds such as glucose, ethanol, formic acid, and the like are preferably added to the reaction system. Thus, these compounds are metabolized by a host, and NAD(P)H generated in the metabolic processes can be used in the reaction.

In the above-described regeneration method (2), as the regeneration enzymes, microorganisms containing those regeneration enzymes, or products prepared from microbial bodies of those microorganisms, such as those prepared by acetone treatment, freeze-drying, and physical or enzymatic disruption, may be used. Moreover, fractions containing the enzymes separated as crudely or finely purified materials from the products prepared from the microbial bodies, those immobilized on a carrier such as polyacrylamide gel or carrageenan gel, and the like may be used. Furthermore, commercially available products of the enzymes may be used.

In the above-described regeneration methods (2) and (3), a compound as a substrate for any of the regeneration enzymes is preferably added to allow the regeneration enzyme to exert its ability to reduce the coenzyme. For example, glucose, formic acid, and an alcohol such as ethanol or isopropanol are preferably added when a glucose dehydrogenase, a formic acid dehydrogenase, and an alcohol dehydrogenase are used, respectively.

As the cells containing the enzymes which catalyze the respective reaction steps, microorganisms inherently having these enzymes may be used, but it is preferred to use cells transformed with DNAs encoding the respective enzymes. In Scheme (i-1), it is preferred to use cells transformed with different DNAs encoding at least one enzyme selected from the group consisting of an L-amino acid oxidase, an L-amino acid dehydrogenase and an L-amino acid transferase, and an N-methyl-L-amino acid dehydrogenase (NMAADH). Moreover, in Scheme (i-2), it is preferred to use cells transformed with different DNAs encoding at least one enzyme selected from the group consisting of a D-amino acid oxidase, a D-amino acid dehydrogenase and a D-amino acid transferase, an amino acid racemase, and an N-methyl-L-amino acid dehydrogenase (NMAADH).

Moreover, each of these DNAs may be integrated into a chromosome, or these DNAs may be introduced into a single vector for use in transformation of a host, or each of these DNAs may be separately introduced into a vector for use in subsequent transformation of a host.

The transformation method for a host cell, such as a microorganism, the type of the host, and the like are the same as those as described above for the L-pipecolic acid hydroxylase.

The second method of producing L-pipecolic acid from L-lysine in the present invention is a production method as described below, the production method characterized by:

(ii) allowing L-lysine to react with one or more enzymes selected from the group consisting of an L-lysine 6-oxidase, an L-lysine 6-dehydrogenase and an L-lysine 6-aminotransferase, for the production of 2,3,4,5-tetrahydropyridine-2-carboxylic acid; and subsequently

allowing a pyrroline-5-carboxylate reductase to act on the 2,3,4,5-tetrahydropyridine-2-carboxylic acid for the production of L-pipecolic acid.

The method will be described below by illustrating a scheme.

First, the compound (a) (L-lysine) is converted to the compound (b′) by at least one enzyme selected from the group consisting of an L-lysine 6-oxidase, an L-lysine 6-dehydrogenase and an L-lysine 6-transferase. The compound (b′) is spontaneously converted to the compound (c′) (2,3,4,5-tetrahydropyridine-2-carboxylic acid). Then, the compound (c′) is converted to the compound (d) (L-pipecolic acid) by a pyrroline-5-carboxylate (P5c) reductase.

The L-lysine 6-oxidase is not particularly limited as long as it is an enzyme which can catalyze the substitution of the amino group at position 6 of L-lysine with an oxo group, but examples of the L-lysine 6-oxidase include LodA described in Biochim. Biophys. Acta., 2006, 1764, pp. 1577, or proteins each having an amino acid sequence with an identity of not less than 80%, preferably not less than 90%, and more preferably not less than 95% to the amino acid sequence of LodA and maintaining the activity thereof.

The L-lysine 6-dehydrogenase is not particularly limited as long as it is an enzyme which can catalyze the substitution of the amino group at position 6 of L-lysine with an oxo group, but examples of the L-lysine 6-dehydrogenase include a protein containing an amino acid sequence as described in J. Biochem., 105, pp. 1002-1008 (1989), or proteins each having an amino acid sequence with an identity of not less than 80%, preferably not less than 90%, and more preferably not less than 95% to the amino acid sequence of the above protein and having the activity thereof.

The L-lysine 6-transferase (lysine-6-aminotransferase) is not particularly limited as long as it is an enzyme which can catalyze the substitution of the amino group at position 6 of hydroxy-L-lysine with an oxo group, but examples of the L-lysine 6-transferase include a protein containing an amino acid sequence as described in WO2001/048216, or proteins each having an amino acid sequence with an identity of not less than 80%, preferably not less than 90%, and more preferably not less than 95% to the amino acid sequence of the above protein and having the activity thereof.

The pyrroline-5-carboxylate (P5C) reductase is not particularly limited as long as it is an enzyme which can catalyze the conversion of 2,3,4,5-tetrahydropyridine-2-carboxylic acid to L-pipecolic acid, but examples of the pyrroline-5-carboxylate (P5C) reductase include a protein containing an amino acid sequence as described in WO2001/048216, or proteins each having an amino acid sequence with an identity of not less than 80%, preferably not less than 90%, and more preferably not less than 95% to the amino acid sequence of the above protein and having the activity thereof.

In the reaction of the production method for pipecolic acid (ii), each step of the enzyme reaction may be separately performed, but it is preferred to sequentially perform the enzyme reaction steps in the same reaction system. In particular, it is preferred to perform the reaction by allowing cells containing the enzymes, which catalyze the respective reaction steps, to react with L-lysine. As the cells containing the enzymes which catalyze the respective reaction steps, cells inherently having these enzymes may be used, but it is preferred to use cells transformed with DNAs encoding the respective enzymes. Specifically, it is preferred to use cells transformed with different DNAs encoding at least one enzyme selected from the group consisting of an L-lysine 6-oxidase, an L-lysine 6-dehydrogenase and an L-lysine 6-transferase, and a pyrroline-5-carboxylate (P5C) reductase.

The transformation method for a host cell, such as a microorganism, the type of the host, and the like are the same as those as described above for the L-pipecolic acid hydroxylase.

In cases where the second method (ii) is carried out continuously in the same reaction system, the method is preferably carried out in an aqueous medium containing L-lysine and cells transformed with a group of genes encoding the respective enzymes, products prepared from the transformants, and/or culture liquids obtained by culturing the transformants, or alternatively in a mixture of the aqueous medium and an organic solvent.

The third method of producing L-pipecolic acid from L-lysine in the present invention is a production method as described below, the production method characterized by:

(iii) allowing a lysine cyclodeaminase to act on L-lysine for the production of L-pipecolic acid.

The lysine cyclodeaminase is not particularly limited as long as it is an enzyme which can catalyze the conversion of L-lysine to L-pipecolic acid, but examples of the lysine cyclodeaminase include a protein containing an amino acid sequence as described in Biochimie 2007, 89, pp. 591, or proteins each having an amino acid sequence with an identity of not less than 80%, preferably not less than 90%, and more preferably not less than 95% to the amino acid sequence of the above protein and having the activity thereof.

It is preferred to perform the reaction by the lysine cyclodeaminase by allowing cells containing a lysine cyclodeaminase to react with L-lysine. As the microorganism containing a lysine cyclodeaminase, cells inherently having the enzymes may be used, but it is preferred to use a cell transformed with a DNA encoding a lysine cyclodeaminase.

The transformation method for a host cell, such as a microorganism, the type of the host, and the like are the same as those as described above for the L lysine L pipecolic acid hydroxylase.

In cases where the conversion of L-lysine to L-pipecolic acid by a lysine cyclodeaminase is performed, the conversion is preferably performed in an aqueous medium containing L-lysine and cells transformed with a DNA encoding a lysine cyclodeaminase, a product prepared from the transformant, and/or a culture liquid obtained by culturing the transformant, or alternatively in a mixture of the aqueous medium and an organic solvent.

In the present invention, the L-pipecolic acid hydroxylase, the microorganism or cell having the ability to produce the enzyme, the processed product of the microorganism or cell, or the culture liquid comprising the enzyme and obtained by culturing the microorganism or cell can be contaminated with L-proline. In that case, the content of L-proline is not more than 10% (w/w), preferably not more than 1% (w/w), and particularly preferably not more than 0.1% (w/w).

Moreover, the microorganism or cell having the ability to produce an L-pipecolic acid hydroxylase may be a microorganism or cell having the ability to produce L-proline from an ingredient as a base material in the culture liquid or the reaction system.

Moreover, a solvent may be used when a hydroxy-L-pipecolic acid is produced. The solvent is not particularly limited, but the production of a hydroxy-L-pipecolic acid is preferably carried out in an aqueous solvent, or in a mixture of an aqueous solvent and an organic solvent.

Examples of the aqueous medium include water or buffers. Examples of the buffer include phosphate buffer, acetate buffer, borate buffer, Tris-HCl buffer, and the like.

Moreover, as an organic solvent to be used in the mixture, an organic solvent such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, tert-butanol, acetone, or dimethyl sulfoxide, in which the solubility of the reaction substrate is high, may be used, while an organic solvent such as ethyl acetate, butyl acetate, toluene, chloroform, or n-hexane, which is effective in the removal of reaction by-products, and the like, may also be used.

The volume of the solvent is not particularly limited, but it is a volume normally in the range of 0.01% (w/v) to 90% (w/v), and preferably in the range of 0.1% (w/v) to 10% (w/v), to the L-pipecolic acid as the substrate.

The concentration of the L-pipecolic acid as the substrate in the reaction system is normally in the range of 0.01% (w/v) to 90% (w/v), and preferably in the range of 0.1% (w/v) to 30% (w/v). The L-pipecolic acid may be added in one portion to the reaction system when the reaction is initiated, but is desirably added to the reaction system in a continuous or intermittent fashion in view of the inhibitory effect on the substrate of the enzyme, if any to be reduced, the increase in the concentration of the accumulated product, and the like.

The amount of 2-oxoglutaric acid to be added is an amount equimolar to or greater than that of the L-pipecolic acid as the substrate, and is preferably an amount ranging from 1 to 1.2 times the number of moles of the L-pipecolic acid as the substrate. The 2-oxoglutaric acid may be added in one portion to the reaction system when the reaction is initiated, but is desirably added to the reaction system in a continuous or intermittent fashion in view of the inhibitory effect on the substrate of the enzyme, if any, to be reduced, the increase in the concentration of the accumulated product, and the like.

Moreover, an inexpensive compound that can be metabolized by the host, such as glucose, may be added instead of 2-oxoglutaric acid to the reaction system, which compound is metabolized by the host and the resulting 2-oxoglutaric acid produced during this process may be allowed to exist in the reaction system.

The concentration of ferrous ion in the reaction system normally from 0.0001 to 0.5 mol, preferably from 0.001 to 0.1 mol, per mol of L-pipecolic acid.

The ferrous ion may be added in one portion, normally in the form of ferrous sulfate, ferrous chloride, ferrous citrate, and the like, to the reaction system when the reaction is initiated. When the added ferrous ions are oxidized to ferric ions or precipitated during the reaction and the level of ferrous ions is thus decreased, it is also effective to add an additional amount of ferrous ion until a desired concentration is achieved.

Moreover, in cases where ferrous ions have already been contained at a desired concentration in the L-pipecolic acid hydroxylase of the present invention, the microorganism or cell having the ability to produce the enzyme, the processed product of the microorganism or cell, and/or the culture liquid comprising the enzyme and obtained by culturing the microorganism or cell, the addition of ferrous ion is not necessarily required.

The reaction is carried out at a reaction temperature of normally 4° C. to 60° C., preferably 15° C. to 45° C., and particularly preferably 20° C. to 40° C., and at a pH of normally 3 to 11, preferably 5 to 8. The reaction time is normally about 1 hour to about 150 hours.

The L-pipecolic acid hydroxylase, the microorganism or cell having the ability to produce the enzyme, the processed product of the microorganism or cell, and/or the culture liquid comprising the enzyme and obtained by culturing the microorganism or cell are/is in such an amount that, for example, the concentration of the microorganism or cell in the reaction system is normally in the range of 0.1% (w/v) to 50% (w/v), preferably 1% (w/v) to 20% (w/v), in terms of wet cell weight if the microorganism or cell is used. Moreover, if the processed product or the culture liquid is used, the processed product or the culture liquid is used in an amount based on the calculated specific activity of the enzyme, which corresponds to the concentration of the microorganism or cell in the reaction system as described above.

Produced hydroxy-L-pipecolic acids can be purified as follows: after the completion of the reaction, microbial bodies, proteins and the like in the reaction system are separated by centrifugation, membrane filtration, and the like; a hydroxy-L-pipecolic acid is subsequently purified by an appropriate combination of extraction with an organic solvent, such as 1-butanol, tert-butanol, or like; distillation; column chromatography using an ion exchange resin, silica gel and the like; isoelectric precipitation; crystallization with a salt, such as monohydrochloride salts, dihydrochloride salts and calcium salts; and the like.

EXAMPLES

Now, the present invention will be described in more detail by way of examples but is not limited thereto.

<Example 1> Cloning of L-Pipecolic Acid Hydroxylase Genes

A gene encoding the amino acid hydroxylase McPH (GenBank Accession No. WP_030487089; SEQ ID NO: 2), which is annotated as an aspartyl beta-hydroxylase derived from a Micromonospora chokoriensis strain, was artificially synthesized as a gene sequence codon-optimized for expression in E. coli (mcph_OE; SEQ ID NO: 1). The gene was inserted into pJExpress411 (DNA2.0) to construct the plasmid pJ411McPH.

Similarly, four genes for enzymes exhibiting the activity to catalyze the hydroxylation of L-pipecolic acid at position 5 were cloned.

The codon-optimized gene sequences sruph_OE (SEQ ID NO: 3), caph_OE (SEQ ID NO: 5), and xdph_OE (SEQ ID NO: 7) for expression in E. coli, which respectively encode the L-pipecolic acid cis-5-hydroxylase SruPH (GenBank Accession No. EFV12517; SEQ ID NO: 4) derived from the Segniliparus rugosus strain ATCC BAA-974, the L-proline cis-4-hydroxylase CaPH (GenBank Accession No. WP_012787640; SEQ ID NO: 6) derived from the Catenulispora acidiphila strain NBRC 102108, and the L-proline cis-4-hydroxylase XdPH (GenBank Accession No. CDGl16639; SEQ ID NO: 8) derived from the Xenorhabdus doucetiae strain FRM16, were artificially synthesized.

The respective genes were inserted into pJexpress411 (manufactured by DNA2.0) and obtained as plasmids, which were named pJ411 SruPH, pJ411CaPH, and pJ411XdPH.

The codon-optimized gene sequence smph_OE (SEQ ID NO: 9) for expression in E. coli, which encodes the L-proline cis-4-hydroxylaseSmPH (GenBank Accession No. CAC47686; SEQ ID NO: 10) derived from the Sinorhizobium meliloti strain 1021, was artificially synthesized and inserted into pJexpress401 to produce the plasmid pJ401SmPH. For the smph_OE, the primers smph_f (SEQ ID NO: 21) and smph_r (SEQ II) NO: 22) were synthesized and used for PCR reaction using the plasmid DNA as a template according to a conventional method to obtain a DNA fragment with a length of about 1.0 kbp. The obtained DNA fragment was digested with the restriction enzymes Nde I and Hind III and then ligated according to a conventional method into pET24a (Novagen) digested with Nde I and Hind III to obtain pEI24SmPH.

A gene encoding the amino acid hydroxylase KjPH (GenBank Accession No. WP_046758372; SEQ ID NO: 18), which is annotated as a hypothetical protein derived from a Kordia jejudonensis strain, was artificially synthesized as a gene sequence codon-optimized for expression in E. coli (kjph_OE; SEQ ID NO: 17). The gene was inserted into pJExpress411 (DNA2.0) to construct the plasmid pJ411KjPH.

Moreover, three genes for enzymes exhibiting the activity to catalyze the hydroxylation of L-pipecolic acid at position 4 were cloned.

The codon-optimized gene sequences cgph_OE (SEQ ID NO: 11), pcph_OE (SEQ ID NO: 13), and gzph_OE (SEQ ID NO: 15) for expression in E. coli, which respectively encode the L-pipecolic acid trans-4-hydroxylase CgPH (GenBank Accession No. ELA34460; SEQ ID NO: 12) derived from Colletotrichum gloeosporioides strain Nara qc5, the L-pipecolic acid trans-4-hydroxylase PcPH (GenBank Accession No. XP_002558179: SEQ ID NO: 14) derived from the Penicillium chrysogenum strain Wisconsin 54-1255, and the L-pipecolic acid trans-4-hydroxylase GzPH (GenBank Accession No. XP 383389; SEQ II) NO: 16) derived from the Gibberella zeae strain PH-1, were artificially synthesized.

Details about the above-described cloned L-pipecolic acid hydroxylases are shown in Table 1.

TABLE 1 SEQ ID NO. ID Microorganism of origin Accession No. 2 McPH Micromonospora chokoriensis WP_030487089 4 SruPH Segniliparus rugosus ATCC EFV12517 BAA-974 6 CaPH Catenulispora acidiphila WP_012787640 NBRC102108 8 XdPH Xenorhabdus doucetiae FRM16 CDG16639 10 SmPH Sinorhizobium meliloti 1021 CAC47686 12 CgPH Colletotrichum gloeosporioides ELA34460 Nara gc5 14 PcPH Penicillium chrysogenum XP_002558179 Wisconsin 54-1255 16 GzPH Gibberella zeae PH-1 XP_383389 18 KjPH Kordia jejudonensis WP_046758372

<Example 2> Obtainment of L-Pipecolic Acid Hydroxylase Gene-Expressing Bacteria

Each of the plasmids obtained in Example 1 was used to transform E. coli (Escherichia coli) BL21 (DE3) (manufactured by Invitrogen) according to a conventional method and thus to obtain the recombinant E. coli BL21 (DE3)/pJ411McPH, BL21 (DE3)/pJ411SruPH, BL21 (DE3)/pJ411CaPH, BL21 (DE3)/pJ411XdPH, BL21 (DE3)/pET24SmPH, BL21 (DE3)/pJ411CgPH, BL21 (DE3)/pJ411PcPH, BL21 (DE3)/pJ411GzPH, and BL21 (DE3)/pJ411KjPH.

To obtain bacteria expressing each of the introduced genes, each recombinant E. coli strain was cultured using liquid LB medium containing kanamycin and a lac promoter-inducible substance for about five hours at 30° C. and then for about 30 hours at 18° C., followed by harvest of the bacteria.

Each of the obtained recombinant E. coli strains in a volume of 0.6 mL was recovered by centrifugation and was suspended in 0.5 mL of 50 mmol/L MES (2-morpholinoethanesulfonic acid) buffer at pH 6. The container containing the suspension was placed in ice-water bath to perform sonication and then spun at 12,000 rpm. The obtained supernatant was used as an enzyme solution in Example 3.

<Example 3> Determination of the Catalytic Efficiency (Kcat/Km) of the L-Pipecolic Acid Hydroxylase with L-Pipecolic Acid and L-Proline

Several L-pipecolic acid hydroxylases were examined for the catalytic efficiency with L-pipecolic acid and L-proline.

To a plastic tube, L-pipecolic acid at a final concentration ranging from 0.3 mmol L to 50 mmol/L, 2-oxoglutaric acid at 20 mmol/L, L-ascorbic acid at 1 mmol/L, ferrous sulfate (II) at 0.5 mmol/L, and each enzyme solution obtained in Example 2 at a protein concentration of about 2 mg/mL were added; then, the obtained reaction solution in a volume of 0.2 mL was shaken at 30° C. for 25 minutes. Subsequently, 0.05 mL of 1 mol/L hydrochloric acid was added to stop the reaction.

The reaction using L-proline as a substrate was carried out under the same conditions as in the above reaction using L-pipecolic acid.

Then, each reaction solution was treated using 1-fluoro-2,4-dinitrophenyl-5-L-alaninamide (FDAA) (manufactured by Tokyo Chemical Industry Co., Ltd.) according to a method as described below, to obtain a FDAA-derivative of a hydroxy-L-pipecolic acid or hydroxy-L-proline included in each reaction solution.

To the reaction solution after stopping the reaction, 0.05 mL of 1 mol/L sodium hydroxide was added for neutralization. After centrifuging the solution at 12,000 rpm, 15 μL of 0.5 mol/L borate buffer (pH 9) was added to 15 μL of the obtained supernatant, followed by further addition of 30 μL of 20 mmol/L FDAA solution in acetone and incubation at 40° C. for one hour. Subsequently, 10 μL of 1 mol/L hydrochloric acid was added to stop the derivatization reaction. The resulting solution was diluted by adding 80 μL of methanol, and then centrifuged at 12,000 rpm. The obtained supernatant was used as a FDAA derivative solution.

The amount of produced hydroxy-L-pipecolic acid or hydroxy-L-proline was analyzed with UPLC-MS (manufactured by Waters Co.). The analytical conditions are shown in Tables 2 to 4.

The (5S)-hydroxy-L-pipecolic acid-producing activity or (4R)-hydroxy-L-pipecolic acid-producing activity (U/mg) indicated by each enzyme solution was defined by units (U) per milligram of each hydroxylase (mg). One unit herein represents the ability to produce 1 μmol of a hydroxy-L-pipecolic acid in the period of 1 minute.

TABLE 2 LC settings Used ACQUITY SQD UPLC/MS (manufactured by Waters instruments Co.) Analytical ACQUITY UPLC BEH C18 Column(manufactured by column Waters Co.) Column temp. 30° C. Eluent A 0.1% formic acid/water solution B 0.1% formic acid/acetonitrile solution

TABLE 3 Elution conditions Time A B Flow rate (min) (%) (%) (ml/min) 0 80 20 0.2 12 45 55 12.5 0 100 14.5 0 100 14.6 80 20 18 80 20

TABLE 4 MS conditions Used instruments SQ Detector (manufactured by Waters Co.) Settings Ion mode ESI Positive Capillary Voltage (kV) 3.0 Cone Voltage (V) 50 Extractor Voltage (V) 3 RF Lens Voltage (V) 0.1 Source Temp. (° C.) 130 Desolvation Temp. (° C.) 350 Desolvation Gas Flow (L/hr) 600 Cone Gas Flow (L/hr) 50

The amount of each hydroxylase was quantified as described below.

An aliquot containing 5 μg of total protein was taken from each enzyme solution obtained in Example 2, loaded on each lane, and then electrophoresed on polyacrylamide gel. The obtained electrophoretogram was analyzed using the image analysis software Image Lab3.0 (manufactured by Bio-Rad Laboratories, Inc.) to determine the content of each hydroxylase. A carbonic anhydrase (manufactured by Sigma-Aldrich Co. LLC) was used as a quantification reference. The content of a hydroxylase of interest was calculated from the signal intensity of the enzyme of interest, based on the signal intensities of bands corresponding to 200 ng, 400 ng and 600 ng of the quantification reference provided for the electrophoresis.

The catalytic efficiency of each enzyme was calculated based on the Michaelis-Menten kinetic equation.

First, the reciprocals of the respective concentrations of L-pipecolic acid (mmol/L) and the reciprocals of the hydroxy-L-pipecolic acid-producing activities per milligram of each hydroxylase (U/mg) at the respective concentrations of L-pipecolic acid were plotted on the x-axis and the y-axis, respectively, where there are four to six data points in the range of 0.3 mmol/L to 50 mmol/L of L-pipecolic acid (FIG. 1). It is known that, in FIG. 1, the reciprocal of each intercept with the x-axis, multiplied with −1, represents a km value (mmol/L) and the reciprocal of each intercept with the y-axis represents a Vmax value (U/mg), the maximum rate of reaction.

The catalytic ability per molecule of the enzyme (kcat) can be calculated from the Vmax and the molecular weight of the enzyme. Table 5 indicates the result of the calculation of catalytic efficiency (kcat/km), which is an index representing the catalytic ability of an enzyme, based on the obtained kcat and km values.

When L-proline was used as a substrate, a much amount of hydroxy-L-proline was detected from the reaction solution using the hydroxylase CaPH. Moreover, a small amount of hydroxy-L-proline was detected from the reaction solutions of the hydroxylases SruPH, XdPH, SmPH, and KjPH. On the other hand, no hydroxy-L-proline was detected from the reaction solution of the hydroxylase McPH. Based on this result, it is understood that McPH is a novel enzyme having the 5-hydroxypipecolic acid-producing activity and characterized by a very low reactivity with proline. This property is not easily deduced from known facts.

Also, no hydroxy-L-proline was detected from the reaction solutions of the hydroxylases CgPH, PcPH, and GzPH. Based on this result, it was found that these hydroxylases were novel enzymes having the 4-hydroxypipecolic acid-producing activity and characterized by a very low reactivity with proline. This property is not easily deduced from known facts.

TABLE 5 A value of the catalytic reaction efficiency for L- Substrate: L-pipecolic acid Substrate: L-proline proline relative to the Vmax Vmax catalytic reaction Molecular Km (U/mg- kcat/ Km (U/mg- kcat/ efficiency for L- Name weight (mM) protein) kcat Km (mM) protein) kcat Km pipecolic acid (5-hydroxy-L-pipecolic acid-producing enzyme) McPH 31872 0.24 0.06 0.03 0.13 (No activity) 0 SruPH 33774 1.09 0.05 0.03 0.02 0.40 0.13 0.07 0.18 754% CsPH 32503 (No activity) 8.87 0.02 0.01 0.00 — XdPH 33475 0.30 1.14 0.64 2.16 0.31 1.44 0.80 2.58 119% SmPH 32019 0.31 0.03 0.02 0.06 0.55 0.06 0.03 0.06 114% KiPH 32277 0.49 0.30 0.16 0.33 0.48 0.34 0.16 0.38 115% (4-hydroxy-L-pipecolic acid-producing enzyme) CgPH 37320 8.56 70.42 43.50 5.12 (No activity) 0 PcPH 32130 3.67 16.16 8.55 2.36 (No activity) 0 GzPH 37835 4.72 114.94 72.48 15.36 (No activity) 0

<Example 4> Comparison of the Reactivity Among L-Pipecolic Acid 5-Hydroxylases

The L-pipecolic acid 5-hydroxylases were compared for the reactivity with L-proline and L-pipecolic acid.

To a plastic tube, L-pipecolic acid or L-proline at 10 mmol/L, 2-oxoglutaric acid at 20 mmol/L, L-ascorbic acid at 1 mmol/L, ferrous sulfate at 0.5 mmol/L, and each enzyme solution obtained in Example 2 at a total protein concentration of about 2 mg/mL were added; then, the obtained reaction solution in a volume of 0.2 mL was shaken at 30° C. for 30 minutes. The amounts of produced hydroxy-L-pipecolic acid and hydroxy-L-proline were determined by the same method based on the derivatization with FDAA as in Example 3. The detection of the products was based on the absorbance at a wavelength of 340 nm.

FIG. 2 shows chromatograms from the LC analysis of the reaction solutions derivatized with FDAA. The activity values were evaluated by the amount of a product per gram of total protein (U/g-protein). The hydroxy-L-proline-producing activity (relative activity) of each sample is presented in Table 6, where a ratio of 100% corresponds to the hydroxy-L-pipecolic acid-producing activity of the same reaction solution.

As indicated in FIG. 2 and Table 6, a much amount of hydroxy-L-proline was detected from the reaction solution of the hydroxylase CaPH. Moreover, a small amount of hydroxy-L-proline was detected from the reaction solutions of the hydroxylases SruPH, XdPH, and SmPH. No hydroxy-L-proline was detected from the reaction solution of the hydroxylase McPH.

Based on this result, it is understood that McPH is a novel enzyme having a high 5-hydroxypipecolic acid-producing activity and characterized by a very low reactivity with proline. This property is not easily deduced from known facts.

Moreover, the hydroxylases SruPH, XdPH, and SmPH were found to be enzymes having a high 5-hydroxypipecolic acid-producing activity and characterized by a low reactivity with proline. This property is not easily deduced from known facts.

TABLE 6 Relative activity (A value of the hydroxy-L-proline-producing activity, where a value of 100 corresponds to the hydroxy-L-pipecolic acid-producing activity) Enzyme Substrate: L-pipecolic acid Substrate: L-proline McPH 100 0 SruPH 100 59 CaPH 100 583 XdPH 100 37 SmPH 100 46

<Example 5> Production of Hydroxy-L-Pipecolic Acids

Eight recombinant E. coli strains obtained in Example 2, that is, BL21 (DE3)/pJ411McPH, BL21 (DE3)/pJ411SruPH, BL21 (DE3)/pJ411CaPH, BL21 (DE3)/pJ411XdPH, BL21 (DE3)/pET24SmPH, BL21 (DE3)/pJ411CgPH, BL21 (DE3)/pJ411PcPH and BL21 (DE3)/pJ411GzPH were inoculated to liquid M9 medium for starter culture (33.9 g/L Na₂HPO₄, 15 g/L KH₂PO₄, 2.5 g/L sodium chloride, 5 g/L ammonium chloride, 10 g/l, casamino acid, 0.1 mmol/L calcium chloride, 0.1 mmol/L ferrous sulfate, 4 g/L glucose, 0.001 mmol/L magnesium chloride) containing kanamycin sulfate (25 μg/mL), and cultured at 30° C. for 24 hours under shaking conditions at 200 rpm.

Forty μL of the culture liquid was added to liquid M9 medium for main culture (50.9 g/L Na₂HPO₄, 22.5 g/L KH₂PO₄, 3.8 g/L sodium chloride, 7.5 g/L ammonium chloride, 10 g/L casamino acid, 0.1 mmol/L calcium chloride, 0.1 mmol/L ferrous sulfate, 20 mmol/L L-pipecolic acid, 12.5 g/L glycerol) containing kanamycin sulfate (25 μg/mL) and Overnight Express Autoinduction Systems (Merck KGaA), and then cultured at 30° C. for 120 hours under shaking conditions at 200 rpm.

Samples for analysis were prepared by collecting and centrifuging the culture 48, 64, and 120 hours after the start of culture, and then recovering the supernatants, and the prepared samples were subjected to LC and MS analyses.

The samples for analysis were treated using FDAA (manufactured by Tokyo Chemical Industry Co., Ltd.) according to a method as described below, to obtain a FDAA-derivative.

After centrifuging the sample solutions for analysis, 27 μL of 0.5 mol/L borate buffer (pH 9) was added to 3 μL of each supernatant, followed by further addition of 30 μL of 20 mmol/L FDAA solution in acetone and incubation at 40° C. for one hour. Subsequently, 10 μL of 1 mol/L hydrochloric acid was added to stop the reaction. The resulting solution was diluted by adding 80 μL of methanol, and then centrifuged at 12,000 rpm. The obtained supernatant was used as a FDAA derivative solution.

The obtained FDAA derivative solution was analyzed for the amounts of a hydroxy-L-pipecolic acid and hydroxy-L-proline under LC/MS conditions indicated in Table 2. The obtained result is shown in FIG. 3 and FIG. 4.

FIG. 3 and Table 7 indicate the result on productivity obtained when (5S)-hydroxy-L-pipecolic acid-producing enzymes are used. FIG. 3 shows the temporal change in amount of accumulated (5S)-hydroxy-L-pipecolic acid. Table 7 shows the accumulation amount of each component determined for the samples of 120 hours post inoculation. It is indicated that almost the entire amount of the substrate was allowed to convert to (5S)-hydroxy-L-pipecolic acid by incubation with the hydroxylases SruPH and McPH for 120 hours.

TABLE 7 Accumulation amount of each component after 120 hours (5S)-Hydroxy- (4S)-hydroxy- Name of L-pipecolic acid L-pipecolic acid L-proline enzyme (mmol/L) (mmol/L) (mmol/L) McPH 23.5 1.8 0 SruPH 22.5 0.1 1.8 CaPH 0.8 18.8 0 XdPH 15.2 10.6 0.3 SmPH 9.4 5.6 0.2

Accumulation of (4S)-hydroxy-L-proline was confirmed in the hydroxylases SruPH, XdPH, and SmPH, in which the reactivity with proline is identified in Example 3. No accumulation of (4S)-hydroxy-L-proline was confirmed in McPH. Also, no accumulation of (4S)-hydroxy-L-proline is confirmed in the hydroxylase CaPH; however, it is likely due to a small capacity of the hydroxylase CaPH as a hydroxylase because the accumulated amount of (5S)-hydroxy-L-pipecolic acid is also small.

Based on these results, it is understood that the hydroxylase McPH is a very practical hydroxylase having a high productivity of (5S)-hydroxy-L-pipecolic acid and characterized by no accumulation of by-products which are hardly removed during the purification steps, such as (4S)-hydroxy-L-proline.

FIG. 4 and Table 8 indicate the result on productivity obtained when (4S)-hydroxy-L-pipecolic acid-producing enzymes are used. FIG. 4 shows the temporal change in amount of accumulated (4S)-hydroxy-L-pipecolic acid. Table 8 shows the accumulation amount of each component determined for the samples of 64 hours post inoculation. It is indicated that a major amount of the substrate was allowed to convert to (4S)-hydroxy-L-pipecolic acid by incubation with the hydroxylases CgPH, PcPH, and GzPH for 64 hours. Moreover, no accumulation of (4R)-hydroxy-L-proline was confirmed.

Based on these results, it is understood that the hydroxylases CgPH, PcPH, and GzPH are very practical hydroxylases having a high productivity of (4S)-hydroxy-L-pipecolic acid and characterized by no accumulation of by-products which are hardly removed during the purification steps, such as (4R)-hydroxy-L-proline.

TABLE 8 Accumulation amount of each component after 64 hours (4S)-hydroxy- (4R)-hydroxy- Name of L-pipecolic acid L-pipecolic acid L-proline enzyme (mmol/L) (mmol/L) (mmol/L) CgPH 19.1 0.2 0 PcPH 17.4 2.1 0 GzPH 18.8 0.2 0

<Example 6> Modification of the Gene for the Hydroxylase McPH Through Mutagenesis

A plasmid encoding a mutant (McPHm1) was constructed using, as a template, the plasmid pJ411McPH obtained in Example 1 as well as using a set of the primer represented by SEQ ID NO: 23 (H4Q-f) and the primer represented by SEQ ID NO: 24 (H4Q-r) indicated in the Sequence Listing, where the QuikChange Multi Site-Directed Mutagenesis Kit (manufactured by Stratagene) was used to replace histidine with glutamine at amino acid position 4.

Plasmids were constructed in the same manner as described above, where a set of the primer represented by SEQ ID NO: 25 (F5Y-f) and the primer represented by SEQ ID NO: 26 (F5Y-r), a set of the primer represented by SEQ ID NO: 27 (C23A-f) and the primer represented by SEQ ID NO: 28 (C23A-r), a set of the primer represented by SEQ ID NO: 29 (C44A-f) and the primer represented by SEQ ID NO: 30 (C44A-r), a set of the primer represented by SEQ ID NO: 31 (L97R-f) and the primer represented by SEQ ID NO: 32 (L97R-r), a set of the primer represented by SEQ ID NO: 33 (V98A-f) and the primer represented by SEQ ID NO: 34 (V98A-r), a set of the primer represented by SEQ ID NO: 35 (D116G-f) and the primer represented by SEQ ID NO: 36 (D116G-r), a set of the primer represented by SEQ ID NO: 37 (C137A-0 and the primer represented by SEQ ID NO: 38 (C137A-r), and a set of the primer represented by SEQ ID NO: 39 (D282E-f) and the primer represented by SEQ ID NO: 40 (D282E-r) were designed and used to replace phenylalanine with tyrosine at position 5 (McPHm2), cysteine with alanine at position 23 (McPHm3), cysteine with alanine at position 44 (McPHm4), leucine with arginine at position 97 (McPHm5), valine with alanine at position 98 (McPHm6), aspartic acid with glycine at position 116 (McPHm7), cysteine with alanine at position 137 (McPHm8), and aspartic acid with glutamic acid at position 282 (McPHm9), respectively.

Each of the obtained plasmids was used to transform E. coli (Escherichia coli) BL21 (DE3) (manufactured by Invitrogen) according to a conventional method and thus to obtain recombinant E. coli strains expressing the respective mutants. Enzyme solutions were prepared according to the method described in Example 2 from the obtained recombinant E. coli strains and evaluated for the activity to catalyze the hydroxylation of L-pipecolic acid at position 5 according to the method described in Example 4. The activity values were evaluated by the amount of a product per gram of total protein (U/g-protein). The activity value (relative activity) of each mutant is presented in Table 9, where a ratio of 100% corresponds to the 5-hydroxy-L-pipecolic acid-producing activity of the wild-type enzyme (McPH) without any mutation.

TABLE 9 Mutated Relative Mutant position activity (Wild type) — 100 McPHm1 H4Q 82 McPHm2 F5Y 132 McPHm3 C23A 123 McPHm4 C44A 0 McPHm5 L99R 18 McPHm6 V100A 2 McPHm7 D116G 27 McPHm8 C137A 42 McPHm9 D282E 152

Furthermore, the combination effect of the respective mutations was examined in the mutations corresponding to McPHm2, McPHm3, and McPHm9, each of which was effective to improve the activity. A plasmid expressing a double mutant (McPHm10) with substitutions of phenylalanine to tyrosine at position 5 and cysteine to alanine at position 23, and a plasmid expressing a triple mutant, which is derived from the double mutant and further has a substitution of aspartic acid to glutamic acid at position 282, were constructed. Then, recombinant E. coli strains were produced according to the method described above, and the resulting enzyme solutions were used to evaluate the 5-hydroxy-L-pipecolic acid-producing activity. The result is presented in Table 10. The triple mutant McPHm11 (SEQ ID NO: 20; a gene encoding the same amino acid sequence is represented by SEQ ID NO: 19) exhibited an activity three or more times higher than that of the wild-type enzyme.

TABLE 10 Mutated position Relative Mutant 1 2 3 activity (Wild type) — — — 100 McPHm10 F5Y C23A — 133 McPHm11 F5Y C23A D282E 314

As for McPHm10 and McPHm11, the hydroxylation activity was determined in accordance with the method described in Example 4, where L-proline was used as a substrate. Thus, virtually no activity against proline was confirmed in both cases. 

The invention claimed is:
 1. A method of producing a hydroxy-L-pipecolic acid, the method comprising: allowing an L-pipecolic acid hydroxylase, a microorganism or cell having the ability to produce the enzyme, a processed product of the microorganism or cell comprising the enzyme, and/or a culture liquid comprising the enzyme and obtained by culturing the microorganism or cell, to act on L-pipecolic acid as a substrate in the presence of 2-oxoglutaric acid and ferrous ion, wherein the L-pipecolic acid hydroxylase has the properties (1) and (2) below: (1) the enzyme can act on L-pipecolic acid in the presence of 2-oxoglutaric acid and ferrous ion to add a hydroxy group to the carbon atom at positions 3, 4, and/or 5 of L-pipecolic acid; and (2) the enzyme has a catalytic efficiency (kcat/Km) with L-proline that is equal to or less than 7 times the catalytic efficiency (kcat/Km) with L-pipecolic acid, wherein the content of L-proline in the L-pipecolic acid as the substrate is not more than 10% (w/w), and wherein the L-pipecolic acid hydroxylase comprises the protein (A), (B), or (C) below: (A) a protein having an amino acid sequence of SEQ ID NO: 18 or 20; (B) a protein having an amino acid sequence with an identity of not less than 95% to the amino acid sequence of SEQ ID NO: 18, which protein has the aforementioned properties (1) and (2); (C) a protein having an amino acid sequence with an identity of not less than 95% to the amino acid sequence of SEQ ID NO: 20 and which comprises at least one of a tyrosine residue at position 5, an alanine residue at position 23 and/or a glutamic acid residue at position 282, which protein has the aforementioned properties (1) and (2).
 2. The method of producing a hydroxy-L-pipecolic acid according to claim 1, further comprising: allowing L-lysine and/or DL-lysine to react with (i-1) one or more enzymes selected from the group consisting of an L-amino acid oxidase, an L-amino acid dehydrogenase and an L-amino acid aminotransferase, or (i-2) an amino acid racemase and one or more enzymes selected from the group consisting of a D-amino acid oxidase, a D-amino acid dehydrogenase and a D-amino acid aminotransferase, for the production of 3,4,5,6-tetrahydropyridine-2-carboxylic acid; and subsequently allowing an N-methyl-L-amino acid dehydrogenase to act on the 3,4,5,6-tetrahydropyridine-2-carboxylic acid for the production of the L-pipecolic acid as the substrate.
 3. The method of producing a hydroxy-L-pipecolic acid according to claim 1, further comprising: allowing L-lysine to react with one or more enzymes selected from the group consisting of an L-lysine 6-oxidase, an L-lysine 6-dehydrogenase and an L-lysine 6-aminotransferase, for the production of 2,3,4,5-tetrahydropyridine-2-carboxylic acid; and subsequently allowing a pyrroline-5-carboxylate reductase to act on the 2,3,4,5-tetrahydropyridine-2-carboxylic acid for the production of the L-pipecolic acid as the substrate.
 4. The method of producing a hydroxy-L-pipecolic acid according to claim 1, further comprising allowing a lysine cyclodeaminase to act on L-lysine for the production of the L-pipecolic acid as the substrate.
 5. The method of producing a hydroxy-L-pipecolic acid according to claim 1, wherein the L-pipecolic acid is contacted with a microorganism or cell having the ability to produce the L-pipecolic acid hydroxylase, and wherein the microorganism or cell having the ability to produce the L-pipecolic acid hydroxylase, or the processed product of the microorganism or cell has a hydroxy-L-proline-producing activity that is not more than 55%, where a ratio of 100% corresponds to the hydroxy-L-pipecolic acid-producing activity of the same microorganism or cell, or of the same processed product.
 6. The method of producing a hydroxy-L-pipecolic acid according to claim 1, wherein the L-pipecolic acid is contacted with a microorganism or cell having the ability to produce the L-pipecolic acid hydroxylase, wherein the microorganism or cell having the ability to produce the L-pipecolic acid hydroxylase is a microorganism or cell transformed with DNA encoding the L-pipecolic acid hydroxylase, and wherein the DNA encoding the L-pipecolic acid hydroxylase comprises the DNA (D), (E), or (F) below: (D) DNA having a nucleotide sequence of SEQ ID NO: 17 or 19; (E) DNA comprising a nucleotide sequence which hybridizes with a complementary strand of the nucleotide sequence of SEQ ID NO: 17 under stringent conditions, wherein the conditions comprise a hybridization at 65° C. in the presence of 0.7 mol/L to 1.0 mol/L sodium chloride aqueous solution and a washing under a temperature condition of 65° C. by using one solution with an SSC concentration of 0.1×SSC (the composition of 1×SSC: 150 mmol/L sodium chloride aqueous solution, 15 mmol/L sodium citrate aqueous solution), which DNA encodes a protein having the aforementioned properties (1) and (2); (F) DNA comprising a nucleotide sequence which hybridizes with a complementary strand of the nucleotide sequence of SEQ ID NO: 19 under stringent conditions, wherein the conditions comprise a hybridization at 65° C. in the presence of 0.7 mol/L to 1.0 mol/L sodium chloride aqueous solution and a washing under a temperature condition of 65° C. by using one solution with an SSC concentration of 0.1×SSC (the composition of 1×SSC: 150 mmol/L sodium chloride aqueous solution, 15 mmol/L sodium citrate aqueous solution), which DNA encodes a protein having the aforementioned properties (1) and (2) and comprising at least one of a tyrosine residue at position 5, an alanine residue at position 23 and/or a glutamic acid residue at position
 282. 